Physicochemical and heavy mineral characterization of soil and groundwater from Ekehuan (Asoro) dumpsite, Benin City

Abstract

Physicochemical and heavy mineral tests were carried out on soil, groundwater, river water, and leachate samples in order determine the negative impact of the dumpsite on soils and groundwater around the Upper Ekehuan (Asoro) dumpsite. A total of forty-two (42) samples consisting of thirty-six (36) soil / sediment, three (3) groundwater, two (2) river water samples (upstream and downstream) and one (1) leachate sample were analysed using Atomic Absorption Spectrophotometer (AAS). The pH analysis revealed values between 6.19-9.21 indicating that the soil tested are slightly acidic to slightly alkaline; while groundwater samples have pH ranges between 5.08-5.58; river water samples have values of pH between 6.52 and 6.55 and leachate has a value of 6.82. The result of soil samples shows that the concentration of Cd (1.83 mg/kg), Cr (6.31 mg/kg), Pb (3.32 mg/kg), Mn (15.04 mg/kg) and Ni (3.39 mg/kg) were much lower than the United States Environmental Protection Agency (USEPA). The soil samples have low to intermediate leaching potentials [(30-49%) - (50-69%) sand fraction]. The average values for Zn, Pb, Cu, Cd, Ni and Cr are lower than the severe effect range of the New York Sediment Criteria and the high effect range of the sediment quality criteria. The World Health Organization (WHO) and Nigeria Standard for Drinking Water Quality (NSDQW) maximum allowed limits were exceeded by the leachate's concentration of heavy metals such Ni, Cd, Cr, Mn, Fe, and Pb as well as turbidity.